Victron output dips when over 35A

[LoudMusic]

I have a new 900Ah lithium install, new 2x350w solar panels, new Victron 100/50 MPPT controller.

If I set the output of the Victron to 35A it will peak at 35A and happily output 35A as long as the Sun is providing enough photons.

If I set it to anything over 35A, even just 36A, it will peak to the set value and within about 15 seconds it will drop to 0A output for a few seconds before ramping up to the set value again, and repeat this cycle.

I've set it to 50A and observed it producing full 50A for the short duration described above both in the VictronConnect app and at my Xantrex battery monitor (minus guestimated usage).

Other settings:

Battery voltage: 12V
Max charge current: 35A
Charger enabled: Yes
Battery preset: User defined
Absorption voltage: 14.60V
Maximum absorption time: 8h 0m
Float voltage: 13.80V
Equalization voltage: 14.40V
Automatic equalization: Disabled
Temperature compensation: Disabled
Low temperature cut-off: Disabled

Has anyone experience behavior like this from a charger, specifically Victron MPPT? Any suggestions on where to start troubleshooting?

[StuM]

BlueSolar or SmartSolar?


Panel specs? Voltage/Current? Parallel or Serial?

[swampbush]

Originally Posted by StuM

BlueSolar or SmartSolar?


Panel specs? Voltage/Current? Parallel or Serial?

The victrons with mc4 connectors are limited to 35 amps per input.

[LoudMusic]

Originally Posted by StuM

BlueSolar or SmartSolar?


Panel specs? Voltage/Current? Parallel or Serial?

SmatSolar 100/50

LG350Q1C-A5 x2 parallel
LG350Q1C-A5

Maximum Power (Pmax) 350
MPP voltage (Vmpp) 36.4
MPP current (Impp) 9.62
Open circuit voltage (Voc) 43.5
Short circuit current (Isc) 10.60
Module efficiency (%) 20.3
Operating temperature (°C) -40 ~ +90
Maximum system voltage (V) 1000
Maximum series fuse rating (A) 20
Power tolerance (%) 0 ~ +3

[pcmm]

Originally Posted by swampbush

The victrons with mc4 connectors are limited to 35 amps per input.

I'll bite... How does the controller know what type of panel connector you are using. Is it a default somewhere?

[swampbush]

Originally Posted by pcmm

I'll bite... How does the controller know what type of panel connector you are using. Is it a default somewhere?

The victrons have either one screw terminal or two or three mc4 connectors on them. So for 150/100 regulator it will have either on large terminal or 3 mc4 terminals. If you try to put more than 35 amps through one terminal it shuts down or limits it seemingly dependent on the amount of overload.

[LoudMusic]

Originally Posted by swampbush

The victrons have either one screw terminal or two or three mc4 connectors on them. So for 150/100 regulator it will have either on large terminal or 3 mc4 terminals. If you try to put more than 35 amps through one terminal it shuts down or limits it seemingly dependent on the amount of overload.

But that's on the input side. I'm saying it shuts down at 36Amps of output.

Further, it has screw terminals.

[noelex 77]

Is the controller getting enough airflow? The Victron units do not have any active cooling and a MPPT controller running at 35A needs a heat sink that is working well. If it mounted reasonably the most likely explanation is that the controller is defective.

I would try updating the software, if this is not the latest, and /or contact Victron.

For some reason MPPT controllers, even name brands, have a high failure/fault rate.

[LoudMusic]

Originally Posted by noelex 77

Is the controller getting enough airflow? The Victron units do not have any active cooling and a MPPT controller running at 35A needs a heat sink that is working well. If it mounted reasonably the most likely explanation is that the controller is defective.

I would try updating the software, if this is not the latest, and /or contact Victron.

For some reason MPPT controllers, even name brands, have a high failure/fault rate.

I was curious about heat as well, but your comment triggered me to go check it for the first time.

It is mounted against a support wall in the engine room. The engine room stays quite cool when the engine is not running. The heat sink itself is between the controller and the wall, which frankly seems a bad design. The heat sink is not overly hot, but the blue portion of the box is unbelievably hot.

I'll see if I can find a fan for it, and test higher output amps.

I also need to get one of those thermometer gun things so I can get actual readings from stuff like this.

PS: Software was updated the end of last week. I'm an IT guy

[noelex 77]

Originally Posted by LoudMusic

The heat sink is not overly hot, but the blue portion of the box is unbelievably hot.

It should not be getting that hot.

The controller is likely to be reducing its output to keep the temperature within limits.

The question is it overheating because it is defective? Or is there inadequate airflow?

The sort of heatsink on the Victron controller needs a reasonable gap above and below the unit so there is an adequate flow of air. Tough to do in the restricted space of a boat especially when the wiring is connected.

A fan is a good idea, and will help diagnose if this is indeed the problem, but it would be better long term if could do without this.

On my own installation I mounted the controllers on an aluminium section. The aluminium increases the gap between the heatsink and the wall giving better airflow. The aluminum section also provides a little more heat sink area (I used some thermal paste) as well as keeping the wires neat and behind the heatsink.

On my installation the controllers are deliberately underated (a 20A controller for a maximium expected output of under 14 A) but I will check the temperatures tomorrow with a IR thermometer, so you have a baseline of what is normal.

[kryg]

Thanks to Loud music and you noelex.

This exchange is very interesting, as I'm planing to install 4 lithium 100 ah battery's with a Victron 100/50 controller as well. and change my solar panels to 2 x 350 watts. bifocal solar panels Glass both sides it is claimed to give 20% more wattage though reflective light. These panels will be mounted on a roll cage over the helm to take advantage of the surrounding reflective light from boat and water.

I have no experience in making these upgrades, love the challenge and education it gives me. I would like to be included as for me this exchange of experience is informative and helpful.

Q). Is one is better served with one controller per solar panel. So would I be better off say installing say two lesser powerful controllers rated at 20 ah each or one like I had in mind the Victron 100/50 ah unit? If so why? - I'm trying to keep this instillation as simple as I can.



Thanks Guys, Kryg S/V Skoiern IV

Originally Posted by noelex 77

It should not be getting that hot.

The controller is likely to be reducing its output to keep the temperature within limits.

The question is it overheating because it is defective? Or is there inadequate airflow?

The sort of heatsink on the Victron controller needs a reasonable gap above and below the unit so there is an adequate flow of air. Tough to do in the restricted space of a boat especially when the wiring is connected.

A fan is a good idea, and will help diagnose if this is indeed the problem, but it would be better long term if could do without this.

On my own installation I mounted the controllers on an aluminium section. The aluminium increases the gap between the heatsink and the wall giving better airflow. The aluminum section also provides a little more heat sink area (I used some thermal paste) as well as keeping the wires neat and behind the heatsink.

On my installation the controllers are deliberately underated (a 20A controller for a maximium expected output of under 14 A) but I will check the temperatures tomorrow with a IR thermometer, so you have a baseline of what is normal.

[john61ct]

Originally Posted by kryg

Is one is better served with one controller per solar panel. So would I be better off say installing say two lesser powerful controllers rated at 20 ah each or one like I had in mind the Victron 100/50 ah unit? If so why?

Yes

1. optimal shade handling.
2. each panel / string gets its own dedicated MPPT optimization
3. redundancy

But panel should be selected to optimize the SC, or v/v.

e.g 75/15 ideal with a 40-65Voc panel rated for 200+W, up to say 280W if a great deal fits the available space right.

Highest W/sq cm is another important consideration with limited space.

[Training Wheels]

I’m thinking of purchasing 2 of the Victron 100/50 controllers. In their manual though, it says for panels in parallel the panels should have a minimum of 36 cells each. My panels have 32 cells with a Voc of 21.6V. Anybody know if the controllers would work?

[noelex 77]

I checked some temperatures today. The Victron units are running warmer than I would have expected especially considering the low ambient temperatures, my added heatsinking, reasonably good ventilation, and the underrated nature of the installation (a 20A controller for a maximum 14A output).

I only had chance to measure the temperature on a couple of occasions so I can imagine the peaks may well be much higher than this.

The air temperature was 20°c. It is not possible to measure the temperature at back of heatsink with the unit installed. The side of the heatsink was only 25°c, but the front blue plastic was reading 41°c at the warmest spot. I can imagine the electonics inside the unit, under the plastic cover, must be considerably hotter than this to raise the outside temperature this much.

These temperatures are a long way below where you would be concerned, but in hot conditions with a unit that was operating at close to peak rated capacity I would try and ensure the installation provided as much cooling as possible.

[noelex 77]

Originally Posted by kryg

Q). Is one is better served with one controller per solar panel. So would I be better off say installing say two lesser powerful controllers rated at 20 ah each or one like I had in mind the Victron 100/50 ah unit? If so why? - I'm trying to keep this instillation as simple as I can.

Generally one controller per panel will be more efficient and adds some redundancy. It depends on the exact specifications, but with Victrons pricing multiple smaller controllers are often not much more expensive than a larger single unit.

The only limitation is the the units desire to drop to float when the current is less than one amp is a little frustrating when running multiple controllers. I hope Victron include the option to disconnect this feature in future software updates. I will need some more time with system to see how often this feature is reducing the effective power output.

You also need to be careful with the relatively high start up voltage. It is not clear if this is a practical problem when using “12v” panels (I suspect not). My panel voltage is high enough, as is yours, that this not an issue in my installation but it may be in others.